Process of manufacturing electric insulating molded articles



' FRITZ em'INwALD, or'rozsoNY, HUNGARI.

'rnocnss or MANUFACTURING ELECTRIC INSULATING Moiinnn ARTICLES.

No Drawing.

To all whom it may concern: Be it known that -I, Dr. FRITZ GRi'INWALD,

a subject of the Emperor of Austria, residing in Pozsony, .,Hungary,have invented a certain new andus'eful Process of Manufacturing ElectricInsulating Molded Articles,

' of which the following is a specification.

It has already been proposed to manufacture molded blocks for electricinsulating purposes of artificial resin, that is to say of 1 theproducts of condensation of phenols and ;or flakes.

met with various difliculties. In mixing the formaldehyde with anaddition of inert substances such as asbestos in the form of fibers Thismanufacture has, however,

constituents, lumps or pasty masses are formed which it is difficult tomold. On rapidly heating the molded articles they are liable to berendered entirely unfit for use because bubbles are formed in the .same,as

' the synthetic resin is liable to undergo a further condensation orpolymerization under the action of heat; now as the articles are heatedfrom the outside this condensation begins at the. surface of thearticles whereby a hard skin is formed, and, as in the course of thecondensation, water is formed which vaporizes at the existingtemperature the hard skin will be broken or severely distorted. :Foravoiding this it has been suggested to heat the articles under pressurebut this greatly reduces the output because for hardening a block ofabout 16 cubic inches in volume it must be left in the'mold underpressure and in the heat for 15 to 20 minutes. Furthermore the waterformed by the continued condensation or polymeriza tion within themolded article can not escape, .so that when the article is subsequentlyheated, as in use, bubbles maybe formed suddenly which may even resultin explo sions. Moreover the electric properties of such molded articlesget poorer in the course of time. I 3 It has also been proposed to heatthe mixture of synthetic resin and inert material very slowly up to atemperature of 100 centigrade for the purpose of preventing both thewater from vaporizing and the outer skin from hardening first. With thismethod, however, several days and even weeks are required for finishingthe molded articles. 1 7 My improved process consists .maddmg tomixtures of synthetic resin and inert ma-- terial from S te 20 per cent.by 'weightLofa Application fil'ed July 3, 1917. Serial No. 178,408.

Specification of Letters Patent. Patented-Feb. 10, 192( carbons, such asbenzol, the boiling tempera ture and vapor tension of which come nearthose of water and in which synthetic resin is insoluble, the mixturesthus become flaky and may be readily molded; the articles-made of suchmixtures are then hardened without anydetriment by heating them rapidlyin the open air.

This is probably due to the fact that. ow-

ing to the pressure of the liquid which amounts to from 5 to 20 percent. by weightof the whole mass the latter is heated uniformlythroughout so that no hard skinor liquid or liquids, such as water, orhydrolaye is formed. Furthermore as the synthetic resin is insoluble inthe liquid it willnot bake or fuse together as lon as there is anyliquid whereby also the loca hardening of the mass is prevented. Theboiling temperature and the vapor tension of the liquid coming very neartothose of water which is formed on heating the molded article from thesynthetic resin this latter water is removed thoroughly and uniformlyany local detrimentalefi'ects resulting therefrom be-- ing avoided. v

A particular example of the process is'as foll6ws:25"'parts ofasynthetic resin inthe plastic state is placed in a mixin machine (forexample, a Werner & P' cider,

mixer) with 40 arts of flaky filling material such 'as asbestos,sawdust, etc., and enoughv water, or a mixture of water and benzin,added until the "mixture becomes in 'g. About 15 arts of water, or ofthe liquid mixture will usually be found to be required. If the mixtureis too stifi, more. water is added if it is too thin, resin and fillingmaterial in'their relative proportions are added.

iii 'llhis mixture is then, as usual in the cold pressing process,placedin molds, the mold ed piecetaken out of the mold and dried andflaky, the mixing being done without heathardenedin an .oven by'heatingat a tem* perature up re 250 0., without any special precautions inregard to the rapidity of the increase of'the temperaturcor the period.of heating.

its

Bythis process l obtain articles of super1or and permanent insulatingproperties, and besides the manufacture of the molded, articles isgreatlyfacilitated and requires far less time than with the oldprocesses above referred to.

overheating of the molded article, and the I claim as my invention:

1. A process of manufacturing electric insulating molded articles from amixture of the products of condensation of phenols and formaldehyde andinert substances consisting in mixing the said condensation products andinert substances with a liquid or liquids in which the condensationprodnets are notsoluble and the boiling point and vapor tension of whichcome near those of water, in then molding the articles and in finallyrapidly heating the molded articles under atmospheric pressure wherebythey are hardened.

2. A process for manufacturing electric insulating molded articles froma mixture of the products of condensation of phenols and formaldehydeand inert substances consisting in mixing the said condensation productsand inert substances with Water, in 20 then molding the articles and infinally rapidly heating them in the open air whereby they are hardened.

In Witness whereof, I have hereunto signed my name in the presence oftwo subscribing witne'sses.

V DR. FRITZ GRUNWALD.

Witnesses:

DIEGO LAsTRAso, IGNATZ SCHAUEN.

